teenagers get frustrated with this because when its said its usually said along the lines of adults saying they where also teens at one point or that teens can get annoying…. sometimes peopel feel like what htey go through others dont know or its hard to describe and when some peole say things like “your acting like a teenager” they feel they are trying to say they know how it feels

That reminds me of a time I was working with another person on seating arrangements for a banquet. I knew some of the people and she knew some of the people. When she would ask me about someone I would say “about my age,” and she would respond, “oh, old.” At the time I was 40.

Because this is typically not exactly said as a compliment. Unless you are telling someone, you are as beautiful and youthful as a teenager (and you are talking to a middle aged woman), it probably will not be perceived as a positive statement.